A Case Study by Dr. Brett Wood DVM, MS, DACVS of Veterinary Referral Hospital of Hickory
Goldie, a 6-year-old female/spayed golden retriever mix, suffered an acute left hindlimb lameness. The owners reported prior intermittent left hindlimb lameness. There was no known trauma. Goldie was reported to be healthy otherwise.
Goldie was evaluated by the VRHOH surgery service. Physical examination revealed a BCS 5/9. General physical examination was within normal limits. Goldie had no signs of significant pyoderma noted. Orthopedic evaluation revealed a Grade IV/IV left hindlimb lameness. There was moderate muscle atrophy of the left hindlimb compared to the right (~ 3 cm difference). There was no evidence of resentment of either coxofemoral joint on manipulation. Examination of the left stifle revealed evidence of effusion and mild medial buttress/ thickening. There was a significant positive drawer/ tibial compression test on extension/flexion. There was no evidence of a persistent meniscal click on manipulation. The right stifle was within normal limits at initial evaluation.
Diagnosis and Discussion of Canine Stifle Disease
Clinical examination was consistent with a cranial cruciate ligament injury. The CCL, known as the anterior cruciate ligament (ACL) in human patients, is one of several ligaments within the knee but is the most important joint stabilizer of the canine knee joint. It originates at the femur and attaches to the forward portion of the tibia. The CCL functions to prevent internal rotation of the tibia and hyperextension of the stifle joint and keeps the tibia from sliding forward during weight bearing (cranial tibial thrust). CCL rupture is a common orthopedic injury in veterinary patients and the most common source of knee problems in all sizes and breeds of dogs.
In humans, injury to the cruciate ligament is usually the result of trauma to the knee. Ligament injury occurs in both the young and old, and athletic and sedentary patient alike, and usually happens during normal activities such as playing ball, running, jumping, etc. In veterinary patients the CCL injury is usually the result of chronic overstressing of the ligament that initially causes a partial injury. In most patients the injury progresses with time to a complete injury. This progression occurs as the ligament, once damaged, has virtually no capacity to heal. The CCL injury results in instability of the stifle joint and secondary meniscal tears and produces knee pain that manifests as lameness. Lameness ranges from mild, weight-bearing lameness to non-weight-bearing lameness.
Treatment Options for Cranial Cruciate Ligament Injury and Discussion
Treatment options were discussed with Goldie’s owner and included both conservative and surgical options. In most dogs greater than 20 pounds or 9 kg, progressive lameness and end-stage severe arthritis is expected in patients that do not have surgery to treat a torn CCL. Markedly decreased activity level, chronic stifle pain, and diminished quality of life are expected endpoints in the vast majority (>90%) of patients that are solely treated medically. In some small patients, conservative management may return them to a reasonable level of activity based on the owner’s expectations. An initial period of conservative therapy, from 4- 6 weeks, may be considered in these pets.
Surgical options discussed with Goldie’s owners included tibial plateau leveling osteotomy (TPLO), tibial tuberosity advancement (TTA), the tightrope procedure, and the augmented lateral suture procedure.
Both osteotomy surgeries, TPLO and TTA, theoretically work by neutralizing tibial thrust to eliminate instability of the stifle. Tibial thrust is caused by the transmission of weight up the tibia and across the knee, which causes the tibia to shift forward relative to the femur. It is because the joint surface of the tibia (tibial plateau) is sloped, not flat, that this cranial tibial thrust occurs. The CCL normally opposes this force, but when torn is incapable of preventing tibial thrust. Pain and lameness is the result.
In vitro cadaver modeling of both techniques reveals that stability is attained with both procedures. However, there is some new data from Europe that the TTA potentially may not stabilize the stifle as well in vivo in up to 80% of patients. Some of the newer techniques for TTA also seem to have an increased complication rate. At this time Dr. Wood is not offering the TTA procedure in any form.
The TPLO procedure neutralizes stifle instability by turning cranial tibial thrust into vertical tibial compression. The TPLO procedure accomplishes the same redirection of vector force by rotating the tibial plateau to a slope parallel to the patellar ligament to neutralize the tibiofemoral shear force. During surgery, a cut is made in the tibia and the bone is then rotated. This produces a flattened or more level plateau that no longer allows forward motion of the tibia. Templating x-rays of the stifle joint are taken before surgery to determine the individual angle and other changes to the individual’s tibia that may affect surgery. After the cut is made in the bone and the plateau angle is leveled, a special bone plate is applied with screws to allow healing.
There are a multitude of other surgical interventions that exist. Many combinations of factors are considered in technique selection including the patient’s:
- Body weight
- Body size
- Current health status
- Pre-injury activity levels
The TPLO technique does seem to optimize recovery of these injuries in the medium- to large-breed patient, those over 40 pounds or 18 kg, and minimize progression of arthritic changes which is especially important in the young or middle-aged patient. In a recent evidence-based-medicine article looking at many objective factors, there was a significant difference in recovery of the TPLO patients long term when compared to the patients with a lateral suture stabilization.
The Tightrope CCL technique was developed with the goal of addressing potential drawbacks of the other techniques, reduction of the complication rate, and potential severity of these complications. The Tightrope CCL technique is based on the lateral suture technique’s principle, which involves placement of a prosthetic material between the femur and tibia to resist forward movement of the tibia. The primary advantages of the Tightrope (TR) over the historical lateral suture technique include bone fixation at both tibial and femoral attachments, more accurate isometric placement, minimally invasive capabilities, and the strength, stiffness, and creep characteristics of the implant. The tightrope implant is placed by first driving k-wires through both the femur and tibia to ensure accurate tunnel locations, followed by overdrilling with a cannulated drill bit over the wires. The Tightrope CCL (fiber tape with toggle and button) implant is then placed through the tunnels and secured to stabilize the stifle. Multicenter data compiled thus far suggests the Tightrope CCL can be performed successfully in medium- and large-breed dogs with CCL deficiency. In patients with excessive tibial plateau angles, greater than 30 degrees, or in giant breed dogs, those over 100 pounds or 45 kg, there may be more appropriate stabilization procedures. Furthermore, in the ongoing multicenter study, 95 percent of “good” to “excellent” outcomes are consistently reported with less than 9 percent complications requiring additional treatment.
The lateral suture is a traditional surgical treatment that has been performed for many years. It may be the oldest technique out of the four. The lateral suture is currently recommended for dogs less than 40 pounds or 18 kg. The concept behind this procedure is to neutralize the stifle laxity, or cranial drawer. A prosthetic ligament is surgicallyimplanted to mimic the function of an intact cranial cruciate ligament. In this technique, one of various suture materials such as monofilament nylon or braided orthopedic fiberwire is placed around the lateral fabella to act as a natural bone anchor and then through a hole drilled in the front of the tibia. These sutures are tightened and either hand-tied to secure the sutures or a crimp system is used. When the patient places weight on the limb, these sutures prevent the abnormal cranial-drawer motion within the joint. With restricted activity, physical therapy, and time, the formation of scar tissue provides long-term stabilization of the joint. If the sutures are over-strained and stretched or torn before adequate scar tissue forms, the function of the knee will be poor due to the reintroduction of joint laxity. To help stabilize these repairs, Dr. Wood typically uses an augmented lateral suture, with placement of a small bone anchor in the femoral condyle, to limit some of the variability related to the fabellar suture placement.
Goldie’s owners decided on the TPLO procedure. Pre-operative CBC and Blood Chemistry was within normal limits. Radiographs of the stifle were obtained. They revealed mild degenerative changes and a moderate amount of effusion. The tibial plateau angle was ~ 27 degrees.
Goldie was placed under anesthesia and exploratory surgery was performed. At surgery she was diagnosed with a complete CCL tear and a large tear of the medial meniscus. A partial medial meniscectomy was performed. A routine TPLO procedure was performed, and the tibial osteotomy was secured in place with a mini-3.5 mm TPLO plate and bone screws after a rotation of ~ 9.5 mm.
Post-operative radiographs revealed a TPLO procedure performed without complication. There was no evidence of implants within the joint space. Post-operative tibial plateau angle was measured at 4 degrees.
Goldie was treated overnight with a fentanyl CRI for pain relief, IV cefazolin, and fluids. The next day, she was started on oral medications carprofen, gabapentin, tramadol, and amoxicillin-clavulinic acid and was discharged for home care with orders for restricted movement. Within 3 days she was starting to bear weight on the affected leg.
Goldie was seen back at VRHOH for her first postoperative visit nine days postoperatively. Orthopedic evaluation revealed that the left stifle incision was clean, dry, and intact. There was no cellulitis, swelling, or edema of the region noted. Goldie was ambulating consistently on the left hindlimb. There was still mild muscle atrophy of the left hindlimb. There was no pain on range of motion manipulation of the left stifle. There was no evidence of medial or lateral patella luxation, crepitus, or instability. The remainder of the orthopedic examination was unchanged from previous evaluation.
Goldie continued to recover with a combination of at-home restriction and physical therapy and was seen for her second postoperative visit eight weeks postoperatively. General physical examination was unchanged from the previous evaluation. The medial left stifle incision region remained clean, dry, and intact. There was no redness, swelling, or localized cellulitis present. Orthopedic evaluation revealed no significant lameness of the left hindlimb at a walking gait. There was still mild muscle atrophy of the left hindlimb. Examination of the left stifle revealed mild thickening, consistent with the previous surgery. There was no pain on range-of-motion manipulation of the stifle. There was no evidence of a reduced range of motion noted. Palpation of the patella tendon revealed no pain on digital palpation. There was no evidence of medial or lateral patella luxation. The remainder of the orthopedic examination was unchanged from previous evaluation. Recheck left-stifle radiographs revealed the tibial osteotomy had healed sufficiently for an early clinical union. There was no evidence of implant failure, migration, or abnormal periosteal proliferation. There did not appear to be evidence of significant progression of secondary osteoarthritic changes. There was no evidence of significant thickening of the distal patella tendon.
Goldie was released with instructions for unrestricted indoor activity and lessening restriction of outdoor activity. Over several weeks she was to return to unrestricted activity. A recheck was recommended should signs of lameness recur.
Evaluation of Postoperative Lameness Following Cranial Cruciate Ligament Treatment
Reinjury of the CCL is rarely a cause of further lameness postoperatively as, in most cases, the ligament is completely ruptured or resorbed by the body and remnants are removed at the time of surgery. Significant lameness due to reinjury after a healed TPLO or tightrope is rare. Occasionally, some dogs develop short-term lameness after a fall or some other form of injury. In the majority of cases, rest and treatment with anti-inflammatory medication results in the return of comfortable limb function in these dogs. However, a sudden and persistent lameness may be related to a secondary, postoperative meniscal injury. Prior to meniscal release, the prevalence of postoperative meniscal tears on canine patients was approximately 15-20%, but with release of the medial meniscus, only a small percentage of dogs, probably 5%, appear to injure their menisci. In many patients, a second-look arthroscopy of the stifle joint can be performed and the meniscal tear removed without the need for an open surgical approach. This greatly reduces post-operative recovery times. Other injuries that are significant enough to require additional surgery in a healed patient are extremely rare. Other potential causes for lameness include other orthopedic conditions such as hip dysplasia, infection or irritation of the implants, progression of arthritis, or, rarely, a primary bone tumor or tumor of the joint.
Clients should be counseled that approximately 30-40% of dogs will rupture the opposite CCL in their lifetime. Patients are screened at the initial evaluation to determine if there is any evidence of bilateral CCL pathology. In the majority of cases, it is usually months to several years between such injuries. Unfortunately, for some patients. the stress of surgery on one stifle exacerbates changes on the other stifle joint; rare patients may have a more accelerated damage that occurs.
For questions about CCL disease or treatment options, please contact Dr. Brett Wood DVM, MS, DACVS at Veterinary Referral Hospital of Hickory at 828-328-6697.